Add SET_SATELLITE_INFO (opcode 77) request + reply body structs

[cameronzucker]

Follows up #26 with the SET_SATELLITE_INFO (BasicCommand 77) payload structs.

SET_SATELLITE_INFO is sent phone → radio while the app is tracking an
amateur satellite. It pushes the current pass solution so the HT can show
az/el/range on its own screen during a pass. (Doppler shift is handled
separately via FREQ_MODE_SET_PAR, not here.)

Wire layout (fixed 30 bytes)

off	size	field	notes
0	20 B	name	satellite name, GB2312, NUL-padded
20	9 b	azimuth	integer degrees 0–359
—	7 b	reserved (0)
—	8 b	elevation	integer degrees (unsigned)
—	8 b	reserved (0)
24	16 b	range_km	slant range, km
26	16 b	altitude_km	orbital altitude, km
28	16 b	countdown_secs	seconds to next event; 0xFFFF = unknown

Bitfields are MSB-first / big-endian, matching the rest of the protocol.

Provenance

The fields come from the BTECH UV Programmer app (com.benshikj.ht.btech.ham):
the serializer w4.d#a() and its caller com.dw.ht.satellite.b#W(), which
computes the look-angle vector via Orekit and rounds az/el/range/altitude into
the fields above. Meanings are cross-checked against the app's embedded
satellite.proto data model (RfInfo/GP/TLE).

Verification

Golden vector — name="ISS", az=180°, el=45°, range=800 km, alt=420 km, countdown=600 s:

49 53 53 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
5A 00 2D 00 03 20 01 A4 02 58

SetSatelliteInfoBody(...).to_bytes() reproduces this byte-for-byte and
round-trips via from_bytes. The countdown_secs sentinel (0xFFFF ↔ None)
round-trips, and SetSatelliteInfoReplyBody encodes a ReplyStatus.SUCCESS
ack to 0x00.

Notes

• Name charset is GB2312 (bf_str(20, "gb2312")), not ASCII — identical for
  typical names (ISS, AO-91, SO-50), diverging only on non-ASCII.
• Firmware clamps range_km/altitude_km > 65535 to 0 (not a sentinel).
• The reply body is inferred, not captured. Every SET_* command in this
  protocol returns a bare ReplyStatus ack (modeled here on
  SetPhoneStatusReplyBody), and the decompile contains no dedicated reply
  parser. The request body is the verified contribution; the reply struct can
  be dropped from this PR if confirming it against an on-air BLE/RFCOMM capture
  first is preferable.